The brake caliper in a disc brake is generally arranged straddling the outer peripheral margin of a brake disc, adapted to rotate around a rotation axis defining an axial direction (X-X). Moreover, in a disc brake there is defined a radial direction (R-R) which is substantially orthogonal to said axial direction (X-X) and intersects it, and a tangential or circumferential direction (C-C), orthogonal both to said axial direction (X-X) and to said radial direction (R-R).
Brake calipers are constrained to a support structure which remains stationary with respect to the vehicle wheel, such as for example an axle-journal of a suspension of a vehicle or a hub of a vehicle wheel.
The brake caliper usually comprises a caliper body comprising two elongated portions arranged facing towards opposite braking surfaces of a brake disc, and at least one bridge which projects straddling the disc, which connects said two elongated portions to each other.
In a standard arrangement of a disc brake on a vehicle, a braking surface of the brake disc faces towards the outside of the vehicle, thus defining the vehicle outer side of the disc brake or side facing towards the vehicle wheel, and the opposite braking surface of the brake disc faces towards the vehicle itself, thus defining the side of the disc brake facing towards the vehicle. Therefore, when a brake caliper is mounted on a brake disc, a first elongated portion of the caliper body is on the outer vehicle side, or wheel side, and a second elongated portion of the caliper body is on the side facing towards the vehicle, or vehicle side. Friction pads are provided, arranged between each elongated portion of the caliper body and the facing braking surfaces of the brake disc.
In the fixed caliper bodies associated with fixed discs, both the elongated portion of the caliper body have a cylinder, or a plurality of cylinders, connected to brake fluid intake channeling and adapted to house hydraulic pistons capable of exerting a thrust action on the friction pads facing towards it or them, thus abutting them against the braking surfaces of the disc to exert the braking action on the vehicle.
This braking action on the vehicle exerts a significant friction adapted to create the desired braking torque on the vehicle itself, which friction however simultaneously generates heat which causes an increase in the temperature of the brake disc, the pads and the caliper body, while the braking action urges, thus deforming the caliper body itself.
The simultaneous increase in the temperature of the caliper body and the deformation thereof generates a risk that, if highly overheated, the caliper body deteriorates its mechanical resistance performance.
Of even more significance is the fact that the increase in temperature of the pad and the caliper body may influence the area of the thrust devices, cylinders-pistons, thus affecting the characteristics of the brake fluid in the intake conduits and the cylinder chambers. In extreme cases, there is a risk of boiling the brake fluid itself, thus forming a dangerously compressible gaseous state in the intake conduits or in the chamber formed between the cylinder and piston, the gaseous state no longer being adapted to transfer the braking control to the pistons and therefore to the pads in an adequate manner.
This very dangerous phenomenon is partly resolved using brake fluids with high boiling temperatures, and caliper bodies provided with aeration openings adapted to evacuate calories.
Examples of such solutions are for example known from documents US2011048870 of Ferrari S.p.A., JP2009036212 of SOPHIA KIKAKU KK, EP0710777A2 of Alcon Components Limited.
An example of solution aiming to increase the heat exchange between the caliper body and the air surround the caliper in order to reduce the heat accumulated by the caliper body itself is given by WO2010051135, while this example shows a solution of radiators associated with the support plates of the pads: US2015090543.
In the cases of high performing braking systems, a forced intake device of cooling air which conveys air close to the pads and the ends of the pistons resting on them is associated with the caliper body.
Examples of such solutions are for example known from documents EP1016804A1, EP2284415 and US2008277216A1 to the same Applicant, Freni Brembo S.p.A., GB2520239A to McLaren Automobile Limited, JPH03194226 to NISSAN MOTOR, JP2011241876 to AKEBONO BRAKE IND., EP1610027 to CONTINENTAL TEVES AG & CO OHG, GB2473001A to Alcon Component Limited.
However, these known solutions are highly complex to make, mount and maintain, especially in daily use vehicles, and even more so in high or very high performing vehicles.
Moreover, the need remains strongly felt to evacuate the heat effectively if the caliper body has accumulated heat, despite the cooling obtained with the air intake and circulation.
Indeed, when the heat unfortunately accumulates in the mass of the caliper body, the cooling times thereof in known forms of caliper are quite lengthy, thus exposing the braking system—in the case of repeated braking actions of significant entity—to an even more increased accumulation of heat and an increased risk of the brake fluid boiling and a deterioration of the resistance performance of the material used to make the caliper body.